1. Field of the Invention
The present invention relates to a focus adjusting technique.
2. Description of the Related Art
Hitherto, there is an image pickup apparatus in which feature points representing, e.g., an eye, a nose and a mouth of a human object, are extracted and an AF (autofocusing) area is set by using the extracted feature points. For example, Japanese Patent Laid-Open No. 2004-317699 proposes an image pickup apparatus which can determine a size represented by extracted feature points and set an optimum AF area in accordance with the determined result, and which can calculate the distance up to an object based on the extracted feature points.
However, extracting the feature points of the human object is a time consuming process. In a particular situation specific to a camera, e.g., in continuous shooting, therefore, camera performance deteriorates in some cases as a result of executing the feature point extraction process. To avoid such a deterioration of the camera performance, Japanese Patent Laid-Open No. 2005-223660 proposes a control technique of not executing the feature point extraction process when a continuous shooting mode, i.e., a mode of picking up an object image in a successive manner, is set. Alternatively, in the continuous shooting mode, an area used for detecting the feature points is set to a smaller size than that in a different mode from the continuous shooting mode. That setting reduces a time required for the feature point extraction process.
With the control technique of not executing the feature point extraction process in the continuous shooting mode, however, it is difficult for a camera to recognize a situation of movement of the object during a period of the continuous shooting. Particularly, when the camera includes a system of performing focus adjustment of the contrast detection type in the continuous shooting mode, a focusing operation following to the object cannot be continued any more if the object has moved outside an AF area set for calculating a focus evaluation value (i.e., a focus signal corresponding to image contrast).
Further, with the known technique of performing control to reduce the feature point detection area in order to cut the time required for the feature point extraction process, the following problem occurs. In a situation where the object has moved outside the feature point detection area, the AF area cannot be secured in a following relation to the object. Consequently, the focusing operation following to the object cannot be continued any more.